Re-inoculation from the appendix and recurrent C. difficile infection (CDI)

Trying to find a topic to write a review article in Bio416 Virology, I came across a post on enzyme evolution in the Discount Thoughts blog that led me to a post on the possible functionality of the appendix. Bollinger et al., writing in Journal of Theoretical Biology, propose that the appendix is a tool for creating probiotic biofilms in the large intestine as well as re-inoculating the large intestine in the event of its defloration by, for example, diarrhea. Their argument rests mostly on recent evidence they cite suggesting that the immune system does not operate antagonistically with normal intestinal bacteria. They present an interesting idea. Although from a developmental view Clarkson points out the authors' limited conception of vestigiality, this view is less relevant to the proposed current functions of the appendix.

(One thing I didn't quite follow was the authors' statement that "receptors for secretory IgA that are important for biofilm formation are up-regulated by the presence of secretory IgA." I take this to mean that IgA is a positive feedback loop in the gut. This interpretation would make sense with regard to IBD and Crohn's. It would also help explain the connection between antibiotics and Clostridium difficile infection--if antibody production were partly dependent on the presence of antibodies, immunity would be partly dependent on the presence of bacteria. However, based on the abstracts for the relevant citations, the statement seems like a non-sequitur. Wold and Adlerberth (2000) conclude that mother's IgA results in less gut immune stimulation and lower salivary IgA, while Friman et al. (1996) refer to IgA's role in capturing probiotic E. coli but not IgA receptors. Peterson et al. (2007) agree with Wold and Adlerberth in finding that IgA attenuates the gut inflammatory response.)

Mongolian nomadic herders

The issue raised by Bollinger et al. of re-inoculating the intestines from the appendix put me in mind of a speaker who came to my nursing school last year. Sas Carey, RN, has traveled to Mongolia on several occasions to help build a health database of nomadic reindeer herders as well as to record their indigenous medical practices. Her travels resulted in the creation of a documentary film as well as a non-profit group called Nomadicare.

In her talk, I remember quite distinctly that she spoke about the herders treating chronic appendicitis by drinking liquified animal stool. My thinking at the time was that it makes sense if the intestinal bacteria from the stool compete with the inflammatory bacteria. In the context of Bollinger et al.'s theory, perhaps it is simply a re-balancing of similar gut flora that keeps appendicitis in check rather than allowing it to become acute.

Chronic appendicitis

You may be thinking that you haven't heard of chronic appendicitis, and it's true that in this country we as nurses are taught RLQ pain-appendicitis-surgery. And even as recently as 1998, Van Winter et al. was asking whether it really existed. However, a breif review of the literature shows that it's been accepted: Konstantinidis et al. (2008) found 6.1% of appendectomy cases from chronic symptoms; and Roumen et al. (2008) found that elective appendectomy relieved chronic RLQ pain.

Sgourakis et al. (2008) identified lack of bowel movement as a factor in chronic appendicitis but not blockage, which is interesting since blockage is the usual explanation for acute appendicitis. Do they have a different etiology? If Mongolian reindeer herders spend a lot of time in the saddle or going without food, could this lead to intestinal stasis and inflammation?

Also, if chronic appendicitis comes from stasis rather than blockage, could the infectious bacteria be different? The theory with acute appendicitis is that normal bacterial flora get trapped in the appendix by a blockage and start to infect the appendix wall. Perhaps in chronic appendicitis, it is the abnormal gut bacteria that get into the appendix. This would explain why the appendicitis is not acute (normal and abnormal bacteria are competing) as well as why the reindeer herders' techniques worked (adding more normal gut bacteria as a probiotic to compete with the infection).

And in fact acute appendicitis is not always caused by blockage, either. Brown et al. (2007) report the case of a man who developed appendicitis after Clostridium difficile infection. From a literature review, they conclude this etiology is rare but may be under-diagnosed since mild forms of appendicitis would be treated by antibiotics along with the C.diff while severe C.diff infections of the entire colon might obscure appendicitis.

The appendix and re-current C. difficile infection

If, as Bollinger et al. suggest, the appendix is involved in re-inoculating the intestine with normal intestinal bacterial, could it not also be a factor in re-current cases of C.diff infection? Maroo and Lamont (2006) state that the reasons some patients have recurrent C.diff infections while others do not is not known: stool samples of recovering patients indicate that spores are present in both patients who have re-current infection and those that do not. Reinfection through the fecal-oral route is a best guess. However, if C.diff infection can occur through die-off of normal bacteria, perhaps the appendix can also lose its normal flora, to be replaced by C. difficile and its spores, which subsequently re-infect the intestine.

As Maroo and Lamont show in their review, stool transplant, which they gingerly call fecal bacteriotherapy, is more effective than pure antibiotics for the treatment of C.diff infection. (The route of stool transplant does not seem to be a decisive factor.) As well, pulsed antibiotic treatment is more effective than daily dosing to prevent re-currence. Both these modalities would allow increased growth of competitive bacteria, which suggests that there is still a source of infection to be competed with.

Stool transplant off the steppe

Aas et al. (2003) performed one of the stool transplants reviewed by Maroo and Lamont. In their retrospective study, of 16 patients suffering from re-curring C.diff infections and multiple antiobiotic treatments, only 1 experienced a re-currence of infection following a nasogastric stool transplant.

The procedure used in this study was as follows:

Obtain stool sample less than 6 hrs before the transplantation procedureSelect a stool specimen (preferably a soft specimen) with a weight of 30 g or a volume of 2 cm3Add 50–70 mL of sterile 0.9 N NaCl to the stool sample and homogenize with a household blender. Initially use the low setting until the sample breaks up; then, advance the speed gradually to the highest setting. Continue for 2–4 min until the sample is smooth.Filter the suspension using a paper coffee filter. Allow adequate time for slow filtration to come to an end.Refilter the suspension, again using a paper coffee filter. As before, allow adequate time for slow filtration.Treat with omeprazole capsules (20 mg po) on the evening before and on the morning of the stool transplantationImmediately before the stool transplantation, a nasogastric tube is placed. Radiography should be used to verify that the tube tip position is in the gastric antrum.A total of 25 mL of the transplantation stool suspension is aspirated into a syringe and instilled into the recipient via the nasogastric tubeAfter the stool instillation, the nasogastric tube is flushed with 0.9 N NaCl. The nasogastric tube is then withdrawn.The patient is permitted to resume a normal diet and all customary physical activities immediately after discharge from the gastroenterology clinic.

This is a lot more expensive than I imagine the Mongolian herders' method is, but I suspect it is also a lot more pleasant for the patient.

Anyhow, to sum up: one theory of the appendix is that its purpose is to re-inoculate the intestines after a pathologic (or possibly pathogenic) event like diarrhea; appendicitis (including or especially chronic appendicitis) may be caused by inoculation of the appendix with pathogens; re-current C.diff infection is not explained, but the effectiveness of probiotic treatment suggests a source of re-infection; and, finally, Mongolian herders' traditional treatment of chronic appendicitis with methods proven to be effective in treating re-current C.diff infection suggests a possible connection between the appendix and C.diff.

1 comment:

With greater percent of natives adopting modern food ingestion practices there will always come modern disease states and accompanying classifications. So-called "pathogens" are janitorial in nature. They clean up. Cellular waste accumulates through ingestion of garbage. Here come the garbage cleaners. Nothing like a healthy massive dose of bacteria to speed up the process. On the other hand, we could always get into fancy terminology and act baffled at causative factors of disease. But, then again, who are we kidding anyway? We're underdeveloped, degenerating, modernized cooked-food-eaters. Disease is our very nature :)

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